A lovely image depicting a heart-warming moment between a gorilla and one of her rescuers is the winner of the Wildlife Photographer of the Year People's Choice Award. Nearly 20,000 people voted in the poll, and Canadian photographer Jo-Anne McArthur's shot Pikin and Appolinaire was the favourite.

Winner of the Wildlife Photographer of the Year People's Choice Award: Pikin and Appolinaire by Jo-Anne McArthur, CanadaJo-Anne McArthur

The winning image captures conservation in action, and highlights the connection between humans and our fellow apes. Pikin, the lowland gorilla, was captured and removed from her habitat to be sold for bushmeat before being rescued by Ape Action Africa. Jo-Anne took her intimate photograph as Pikin was being moved to a safe enclosure in Cameroon. She awoke from sedation during the transfer but remained calm for the bumpy drive, resting drowsily in the arms of her human companion, Appolinaire.

Appolinaire Ndohoudou was also forced from his home, due to civil war in Chad. In the process of rebuilding his life, working to protect wild animals has revived his appreciation for the natural world. He has built loving relationships with the gorillas he has helped rear, some of them from infancy.

Jo-Anne says, "I'm so thankful that this image resonated with people and I hope it might inspire us all to care a little bit more about animals. No act of compassion towards them is ever too small. I regularly document the cruelties animals endure at our hands, but sometimes I bear witness to stories of rescue, hope and redemption. Such is the case with the story of Pikin and Appolinaire, a beautiful moment between friends."

Sir Michael Dixon, Director of the Natural History Museum, says, "Like Hope (our blue whale) Jo-Anne's inspirational image is a symbol of humanity's power to protect the world's most vulnerable species and shape a more sustainable future for life on our planet. Photographs like Jo-Anne's are a reminder that we can make a difference, and we all have a part to play in addressing our impact on the natural world."

The Natural History Museum has also named four finalists, which – together with Jo-Anne's winning image – make up the top five pictures in the Wildlife Photographer of the Year People's Choice Award:

Roller rider byLakshitha Karunarathna, Sri Lanka: Lakshitha was on safari in Maasai Mara National Reserve, Kenya, when he spotted an unusual sight – a lilac-breasted roller riding a zebra. Normally they prefer to perch high up in the foliage, but this roller spent an hour or more riding around and enjoying the occasional insect meal. Lakshitha waited for the surrounding zebras to form the perfect background before taking this tight crop.

Elegant mother and calf by Ray Chin, Taiwan: Every year from July to late October southern humpback whales migrate north from their Antarctic feeding grounds to give birth in the warm sheltered waters off Tonga. Ray encountered this humpback mother and calf peacefully floating in the plankton-filled water around the island group of Vava'u, Tonga. After Ray gently approached them, the giants swam a bit closer to have a look at him. While they made this elegant turn, Ray took the shot. He later converted the image into black and white which he felt represented the simplicity of the scene.

Elegant mother and calf by Ray Chin, TaiwanRay Chin

Sloth hanging out by Luciano Candisani, Brazil: Luciano had to climb the cecropia tree, in the protected Atlantic rainforest of southern Bahia, Brazil, to take an eye-level shot of this three-toed sloth. Sloths like to feed on the leaves of these trees, and so they are often seen high up in the canopy.

Sloth hanging out by Luciano Candisani, BrazilLuciano Candisani

Warm embrace by Debra Garside, Canada: When polar bear mothers and cubs emerge from their dens in the early spring, the cubs stay close to their mothers for warmth and protection. Once the cubs are strong and confident enough, they make the trek to the sea ice with their mother so that she can resume hunting for seals. Debra waited six days near the den of this family, in Wapusk National Park, Manitoba, Canada, before they finally emerged. In the most challenging conditions she has ever faced, temperatures ranged from -35˚C (-31˚F) to -55˚C (-67˚F) with high winds, making it almost impossible to avoid frostbite and keep her camera gear functioning properly.

Warm embrace by Debra Garside, CanadaDebra Garside

Wildlife Photographer of the Year is the Natural History Museum's annual showcase of the world's best nature photography and photojournalism. Seen by millions of people all over the world, the images shine a spotlight on nature photography as an art form, whilst challenging us to address the big questions facing our planet. The 2018 competition is currently being judged by an esteemed panel of experts, and the winners will be revealed in October.